The invention relates in particular to a fixed recuperative heat exchange device for use in turbine or Stirling cycle engines.
In a gas turbine engine, an air-fuel mixture is burned in a combustion chamber to form hot gases which are directed to a turbine wheel to produce rotary motion of an engine output shaft. After these gases have impinged upon the turbine wheel, and prior to their being exhausted from the engine, it is desirable to extract as much heat energy as possible. The efficiency of the gas turbine engine is increased by transferring the heat energy extracted from these exhaust gases to the compressed intake air prior to its mixture with the fuel and entry into the combustion chamber. One type of heat exchanger that is used to accomplish this energy transfer and raise the temperature of the incoming compressed air is called a rotary regenerator.
This heat exchange system which employs a rotating cylindrically shaped regenerator core has in the past been found to be suitable for gas turbine engines. Typically, the regenerator core is made from a ceramic material and is porous to gases which flow substantially parallel to the rotational axis of the core. The porous, ceramic regenerator core rotates in a housing that is divided into a plurality of passages. Hot exhaust gases and the cooler compressed imcoming air pass through these passages and through the porous regenerator core. The exhaust gases heat the regenerator core and the regenerator core, in turn, transfers this absorbed heat energy to the cooler compressed incoming air. In this manner, heat transfer results.
As is evident, this type of rotary regenerator unfortunately requires many accessory items to function properly, such as, drive mechanisms, motors and annular ring gears for rotating the core and rubbing seals and special housings for sealing the different sections of the core and the entire core from the rest of the engine. Additionally, material requirements of thermal shock resistance, light weight, rigidity against fluid pressure, strength for rotation drive and sealability severely reduce the field of candidate materials for regenerator use.
The present invention is concerned with a fixed recuperator which does not require movement and therefore does not require the use of all the accessories named. It also enlarges the field of possible materials by eliminating some physical property requirements.
Metal recuperators of the type have been used in the past, for example see U.S. Pat. No. 3,322,189, but they are not capable of being used in very high temperature environments, are difficult and expensive to build, and are cumbersome and inflexible in design, particularly with regard to the flow path of the fluids.
In general, the multiple flow path body of present invention may be used as a recuperator as mentioned above or as a heat exchanger or afterburner to reduce energy requirements for maintaining combustion in industrial ovens for baking, oxidizing, polymerizing or removing coatings, in organic waste incinerators, in foundry cupulos, and in internal combustion engines. In addition to operating as a heat exchanger, it may also be used in filtration and osmosis when porous materials are used to produce the honeycombed body.